Influence of the composition and structure of the glass-crystalline shell of cenospheres on helium permeability

We studied the interrelation between the composition, morphology, and helium permeability of the shell of narrow fractions of nonmagnetic nonperforated cenospheres extracted from cenosphere concentrates of fly ash of the sialic type with the use of technological stages of hydrodynamic, magnetic separation, sizing, and aerodynamic classification. For the interval of variation of Al 2 O 3 content from 20 to 38 wt %, the regression equation [SiO 2 ]/[Al 2 O 3 ] = 5.06 − 0.1[Al 2 O 3 ] is established, with the correlation coefficient equal to −0.98. It is found that, together with the growth in the concentration of Al 2 O 3 in the indicated interval, the content of the originally mullite phase increases from 1.3 to 42.4 wt %, and this is accompanied by the growth of the helium permeability of the glass-crystalline shell of the cenospheres.